This paper examines the context-dependent role of race as a predictor of non-electoral political participation. Prior country-level studies have documented group-level differences in a variety of forms of participation in South Africa and the United States, but have found few to no differences in Brazil. Why are members of one group more engaged in certain political activities than members of other groups only in specific contexts? Why do members of socioeconomically deprived groups, such as non-Whites, participate more than better-off groups in acts that require group mobilization in South Africa and the United States but not in Brazil? Results from the World Values Survey and the International Social Survey Programme show that Blacks and Coloureds in South Africa and Blacks in the United States participate more than Whites in activities that demand prior organization and mobilization, whereas group differences are negligible in Brazil. I argue that (1) race as a driver of political mobilization is conditional on the existence of politicized racial identities; (2) members of groups that share a strong collective identity participate in direct political action more than predicted by their socioeconomic background; (3) politicization of identities is the product of racial projects that deploy the state apparatus to enforce group boundaries for the implementation of segregationist policies as well as the reactions against them; and (4) by enforcing group boundaries, those systems unintentionally create the conditions for the formation of politicized group identities. In the absence of such requisites, political mobilization along racial lines would be weak or nonexistent.